Numerous chemical compounds that are used in industrial applications are prone to oxidative degradation. For example, certain conditions may induce the formation of free radicals in polymers, lubricants, coatings, and the like, which can be detrimental to product quality. Food products and cosmetics that contain oils and lipids may become rancid from oxidation, which can adversely affect the taste and odor of the product. In the metal industry, protective coatings may be used on metals, such as ferrous metals, to prevent corrosion. Hence, manufacturers typically add antioxidizing agents and free radical inhibitors to preserve their products.
However, current preservatives may possess undesirable properties that can lead to other problems. For instance, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are common food preservatives that being scrutinized as endocrine disruptors and carcinogens. As another example, the addition of polymerization inhibitors can prolong the shelf-life of the polymer precursors; but may require an additional process to remove the inhibitors in order to maintain polymer purity. The preservatives can also become exhausted and over time, lose their effectiveness and stability. Hence, novel antioxidant compounds and inhibitors are needed as an alternatively to existing technologies.
This present invention utilizes hydrogenated tetrazines, such as dihydrotetrazines, tetrahydrotetrazines, and hexahydrotetrazines, as antioxidants or free radical reaction inhibitors. Although there exist many antioxidants based on aromatic molecules modified with hydroxyl groups (phenols), amines (aryl amines), or phosphites, there have been no reports on hydrogenated tetrazines being used as antioxidants.
Jaiswal et al. teaches the use of tetrazines as potential coating additives (Jaiswal, S.; Varma, P. C. R.; O'Neill, L.; Duffy, B.; McHale, P., An investigation of the biochemical properties of tetrazines as potential coating additives. Mat Sci Eng C-Mater 2013, 33, (4), 1925-1934). However, said tetrazines are amine-modified tetrazines without the hydrogen atoms, and are essentially an extension of aryl amine antioxidants that rely on single electron transfer chemistry and resonance stabilization of the resulting radical cation for antioxidant stability.
Wang et al. teaches the use of 1,4-dihydropyridine as an antioxidant (Wang, L. F.; Zhang, H. Y.; Kong, L.; Chen, Z. W.; Shi, J. G., DPT calculations indicate that 1,4-dihydropyridine is a promising lead antioxidant. Helv Chim Acta 2004, 87, (6), 1515-1521). However, the 1,4-dihydropyridine compound contains only one nitrogen in the ring and said nitrogen is more difficult to recycle than those in the tetrazines.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.